What is groundwater?

Groundwater comes from rain and snow that soaks into the ground, passing between particles of soil, sand, gravel or rock until it reaches a depth where the ground is filled, or saturated, with water.  The area that is filled with water is called the saturated zone and the top of this zone is called the water table.  The water table may be very near the ground surface or it may be hundreds of feet deep.  Groundwater is stored in the ground in materials like gravel or sand.  You can think of the earth as a big sponge holding lots of water.  An area that holds a lot of water, which can be pumped up with a well, is called an aquifer.